The set-up for Katori Hall’s “The Mountaintop,” by True Colors Theatre Company at the Southwest Arts Center through December 16, is heartbreakingly heavy with the weight of near-mythic history. The two-person, one-act play, written when the young playwright was in her 20s, imagines an encounter between the iconic civil rights leader and a hotel maid in his Memphis hotel room on the eve of his assassination.

The play was an unexpected hit when it premiered at a fringe theater in London in 2009 before moving to the West End. The subsequent 2011 Broadway production starred Samuel L. Jackson and Angela Bassett, under the direction of True Colors Artistic Director Kenny Leon. The Atlanta production, directed by Jasmine Guy, is one of the first regional productions of the play.

What’s so special about “The Mountaintop” is the way Hall uses theater to humanize and particularize broadly historic, almost inaccessibly monumental events. King, we learn, smokes Pall Mall cigarettes behind closed doors, has a problem with smelly feet and is developing a cough.

In the popular imagination, King can become a secular saint: unimaginably distant, iconic, sacred and even inhumanly perfect. Hall’s quiet play crackles with the energy of all the things about him that are kept off to the side and out of the spotlight. There’s a wonderful interplay between the monumental and the mundane that gives “The Mountaintop” its life. It’s a pretty daring act of imagination.

But what eventually emerges about King isn’t just a collection of human flaws but a sense of human complexity. Exhaustion, fear and doubt go hand in hand with the courage, moral strength and certainty we’re all familiar with. Also often forgotten or unmentioned is the fact that at the time depicted, King was becoming much more broadly progressive.

A robust Civil Rights Act had been enacted four years earlier that ended many forms of legal segregation in the United States. By 1968 that particular legal battle was essentially won, and King had turned toward fighting economic inequality and the Vietnam War and for workers’ rights. (He was in Memphis in support of striking sanitation workers.) The fiery speech he was working on at the time of his death was titled, “Why America May Go to Hell.”

The King who exists in the popular imagination is often the King of 10 years earlier. But Hall depicts this later King, someone setting himself to the terrifyingly daunting task of taking on a very broad, seemingly unconquerable set of injustices. Her King seems to feel that he’s very much at the beginning of a struggle, which he knew would eventually take his life one way or another — the familiar, beautiful dream just barely able to peek through a dark and damning jeremiad.

Actor Danny Johnson has been given the massive task of portraying King in King’s hometown. But he slips easily into Hall’s humanizing project. Whether he’s working on a speech, flirting with the hotel maid, smoking a cigarette or torturing himself about a boy who’s been killed by police at a march, Johnson’s King burns with a tough, confident but often self-immolating intensity. It’s also an intensity that’s clearly starting to wear him down. He’s weary, even exhausted. He’s fearful for his life and has been for years. Thunder sounds enough like a bomb or gunfire to make him not just jump, but nearly collapse, to check his body to see if he’s been hit.

Demetria McKinney’s Camae — direct, plain-spoken, cursing with an irrepressible creative enthusiasm — makes a great foil for Johnson’s more guarded King. Their conversation as they share cigarettes and coffee takes in the personal and the political — Malcolm X, King’s family, Vietnam — over the play’s 90 minutes.

The play has an “all is not exactly as it seems” secret that’s hard to talk about in a review without giving too much away. But I can say that the second half, for me, never quite made the spiritual leap it was attempting. I found the chemistry of the two leads far more magical than the bit of magic that metaphorically pokes its head in the door in the latter half.

The revelation also somewhat disrupts the play’s earlier, more interesting idea: Camae and King are vastly different but somehow equally fascinating repositories of American history and ideas. King asks Camae what she would do if she were him, and she responds by putting on his jacket and delivering a mock King speech in which he renounces nonviolence.

It’s a human-sized doorway into huge and historic events, a depiction of how the momentous and the everyday may not be as far apart as we often imagine, bridging the gap between the mythic and the mortal, the human and the divine. It’s what theater is all about. It’s odd to end the play with the gap opening up again. Projections illustrate too literally what should be left as spoken word, and the ascent into oratory (we end with a recitation of a King speech), though beautifully delivered, feels like a return to the inaccessibly grand.

Though “The Mountaintop” is far from perfect, it’s fascinating work from a young playwright at the beginning of a career that will be one to watch.